Question: Simplify the following expression: $k = \dfrac{6}{5a} - \dfrac{1}{7a}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5a$ and $7a$ $\lcm(5a, 7a) = 35a$ $ k = \dfrac{7}{7} \cdot \dfrac{6}{5a} - \dfrac{5}{5} \cdot \dfrac{1}{7a} $ $k = \dfrac{42}{35a} - \dfrac{5}{35a}$ $k = \dfrac{42 -5}{35a}$ $k = \dfrac{37}{35a}$